Pose mode and GRS all give me a scale cursor that doesn't do any thing
Judging from your second screenshot, I'd suppose you've got Manipulate Center Points activated. While this is useful on multiple selected objects or bones, when bones are not connected, it leads to the behavior you describe in your Question. See the GIF below on how to deactivate this feature:



The purpose of this feature is to Translate objects by using Rotate or Scale functions. In your case, as the bone is already a child of another bone, Translation channels are automatically locked already. That's why nothing happens.